The need to conserve water is well known, thus there are many inventions directed at conserving unnecessary water use in flush toilets. A typical conservation apparatus uses two flush modes. The first mode completely empties the toilet tank, while the second mode provides a limited release of less than the complete tank volume to conserve water when less flow is required.
U.S. Pat. No. 1,992,381 to Lyons discloses a flushing valve assembly that provides the option of full or partial flushes. Turning a handle in a first direction raises a lever sufficiently to open a flush valve to provide a full flush. Turning the handle in the opposite direction lifts the lever to partially open the valve, the valve closing immediately when the handle is released. A mechanical connection between the handle and the lever is provided by a pair of links that are pivotally attached between the handle and the lever. The complexity of this linkage, which uses a stop screw for setting the handle travel, is undesirable due to the build-up of minerals and corrosion by-products that typically occurs in a flush tank environment. In addition, the complexity of the linkage and number of parts increases manufacturing costs.
Other existing mechanisms are complex and difficult to install. Thus, they are unsuitable for retro-fit installation in existing toilets, especially by untrained do-it-yourself homeowners.
Other dual flush devices utilizing complex mechanisms are shown in the prior art, and have similar disadvantages as the Lyons reference discussed above. Such devices are shown in the following references:
U.S. Pat. No. 4,391,003 to Talerico et al.
U.S. Pat. No. 4,411,029 to Huang
U.S. Pat. No. 4,485,501 to Kloner
U.S. Pat. No. 4,527,296 to Musgrove
U.S. Pat. No. 4,651,359 to Battle